package backtype.storm.grouping;

import backtype.storm.generated.GlobalStreamId;
import backtype.storm.task.WorkerTopologyContext;
import java.io.Serializable;
import java.util.List;

public interface CustomStreamGrouping extends Serializable {

	/**
	 * Tells the stream grouping at runtime the tasks in the target bolt. This
	 * information should be used in chooseTasks to determine the target tasks.
	 * 
	 * It also tells the grouping the metadata on the stream this grouping will
	 * be used on.
	 */
	void prepare(WorkerTopologyContext context, GlobalStreamId stream,
			List<Integer> targetTasks);

	/**
	 * This function implements a custom stream grouping. It takes in as input
	 * the number of tasks in the target bolt in prepare and returns the tasks
	 * to send the tuples to.
	 * 
	 * @param values
	 *            the values to group on
	 */
	List<Integer> chooseTasks(int taskId, List<Object> values);
}
